Blast freezer problem !!!

hello experts,
i am new member of this forum this is my first post, i am working in food plant as trainee ref. operator i have good knowledge of ref. SOP but not expert yet.
recently in our plant blast freezer has some problem
for personal knowledge update i would request you to suggest me possible causes for the problem.
we have Vilter -R22 compressor, with driven by 25HP motor,
suction pressure 6-7 Psi , discharge is 170-180 PSI
Oil pressure is - 40-45 PSi (normal operation condition)
since yesterday our oil return line ICED Up and discharge line is cold, compressor was running perfect without any error , discharge pressure was OK but suction was high 10-11 PSI , oil pressure reached 55-60 PSI ,
any idea or suggestion !! why this problem created ??
help appreciated , thanks in advance !!!

neel,
I think your oil float has stuck open.
You can give it a tap and see if it reseats,otherwisw it may have dirt/foreign matter under the seat.

Discharge line cold and oil return returning liquid can be from a few things .
Liquid coming into compressor suction line going through compressor , causing low discharge temp and liquid refrigerant in sump from flood back & oil return , or

Compressor is cycling and non return valve in discharge line is leaking , during off cycle condensing refrigerant in oil seperator .
When it starts up it returns it to sump , cold oil so higher oil pressure .

Have a feel around cylinders between head and sump cover area on both sides of machine . Should be warm at least , if it is cold suspect liquid entering from suction side .

As for higher suction pressure
Check above first & s/heat into compressor .

Let us know what you come up with .

The stop/check valve after the oil separator and before the condenser is passing/ leaking, allowing discharge gas to condense in oil separator, which in turn is returned to compressor, at sump pressure, so flashes off and frosts the return line.
Check the check valve for worn seals and broken springs.
magoo

The conditions you describe are related [to my opinion] to the TXV.

When you get liquid in the oil separator, it means the compressor is pumping liquid and thats why the discharge line is cold.
You did not mentioned anything about defrost but i suggest you check the HGSV for leaking or being open while its in cooling mode.

Good luck and please come back with your results.

everybody having a good guest . need a little more info about the system /components. all could be right .

Oil return line frosted and discharge line cold is due to accumulation of R-22 liquid in the oil separator. This happens when there is liquid slugging in the compressor or discharge check valve is defective allowing gas to condense and return back into the oil separator.
Reciprocating compressors can handle small amounts of liquid refrigerant not unlike screw compressors wherein you will hear a "screeching noise" when liquid enters the screw rotors.,but still it is not good practice to let the compressors suck in liquid refrigerant.
Check if your compressor oil separator have built-in heaters to retain the correct oil sump temp. especially during winter season.,but also check the recommendations as advised by our friends above.

hi experts,
i am sorry for late reply bcoz weekends !!
thanks for suggestion !!! and advices
i really appreciate !!!!
whole scenario we had outside contractor for this type of problem and at my level i am small guy but i was with them during whole trouble shooting
they were even not sure why things happing ??
the problem diagnose (true or false i don't know) by them was
electrical problem - loose connection of evaporator fan so evap fan shut off and freeze line, the oil return line was plugged ! and they open compressor to clean and replace brand new oil, they set TXV (little close) so try to reach perfect super heat !!! etc..etc...etc...

since the day everything is fine ...we are keeping eye on it.
as i mention i am trainee still i am trying to understand whole system device and parameter of my plant.
if something new i found i will post here.

again thanks all of you and appreciate your advice and suggestion which help me to understand more things.

In future check system superheats condensor compressor and evaporator this would have directed you to the cause . Superheat readings are essential for good fault finding.